Regulation of proliferation-survival decisions during tumor cell hypoxia.

Hypoxia may influence tumor biology in paradoxically opposing ways: it is lethal as a direct stress trigger, yet hypoxic zones in solid tumors harbor viable cells which are particularly resistant to treatment and contribute importantly to disease relapse. To examine mechanisms underlying growth-survival decisions during hypoxia, we have compared genetically related transformed and untransformed fibroblast cells in vitro for proliferation, survival, clonogenicity, cell cycle, and p53 expression. Hypoxia induces G0/G1 arrest in primary fibroblasts but triggers apoptosis in oncogene-transformed derivatives. Unexpectedly, the mechanism of apoptosis is seen to require accumulated acidosis and is rescued by enhanced buffering. The direct effect of hypoxia under nonacidotic conditions is unique to transformed cells in that they override the hypoxic G0/G1 arrest of primary cells. Moreover, when uncoupled from acidosis, hypoxia enhances tumor cell viability and clonogenicity relative to normoxia. p53 is correspondingly upregulated in response to hypoxia-induced acidosis but downregulated during hypoxia without acidosis. Hypoxia may thus produce both treatment resistance and a growth advantage. Given strong evidence that hypoxic regions in solid tumors are often nonacidotic (G. Helmlinger, F. Yuan, M. Dellian, and R. K. Jain, Nat. Med. 3:177-182, 1997), this behavior may influence relapse and implicates such cells as potentially important therapeutic targets.

Cardiac effects of adjuvant doxorubicin and radiation therapy in breast cancer patients.

PURPOSE: To assess the cardiac effects of two different cumulative doses of adjuvant doxorubicin and radiation therapy (RT) in breast cancer patients. PATIENTS AND METHODS: Two hundred ninety-nine breast cancer patients were prospectively randomized to receive either five cycles (CA5) or 10 cycles (CA10) of adjuvant treatment with cyclophosphamide (500 mg/ m2) and doxorubicin (45 mg/m2) administered by intravenous bolus every 21 days. One hundred twenty-two of these patients also received RT. Estimates of the cardiac RT dose-volume were retrospectively categorized as low, moderate, or high. The risk of major cardiac events (congestive heart failure, acute myocardial infarction) was assessable in 276 patients (92%), with a median follow-up time of 6.0 years (range, 0.5 to 19.4). RESULTS: The estimated risk (95% confidence interval) of cardiac events per 100 patient-years was significantly higher for CA10 than for CA5 [1.7 (1.0 to 2.8) v 0.5 (0.1 to 1.2); P=.02]. The risk of cardiac events in CA5 patients, irrespective of the cardiac RT dose-volume, did not differ significantly from rates of cardiac events predicted for the general female population by the Framingham Heart Study. In CA10 patients, the incidence of cardiac events was significantly increased (relative risk ratio, 3.6; P < .00003) compared with the Framingham population, particularly in groups that also received moderate and high dose-volume cardiac RT. CONCLUSION: Conventional-dose adjuvant doxorubicin as delivered in the CA5 regimen by itself, or in combination with locoregional RT, was not associated with a significant increase in the risk of cardiac events. Higher doses of adjuvant doxorubicin (CA10) were associated with a threefold to fourfold increased risk of cardiac events. This appears to be especially true in patients treated with higher dose-volumes of cardiac RT. Larger studies with longer follow-up periods are needed to confirm these results.

Functional imaging of normal tissues with nuclear medicine: applications in radiotherapy.

Functional imaging techniques are gaining significant interest from radiation oncologists. Many now claim the need for physical and physiological information during both treatment planning and in the study of normal tissue injury. Toward this goal, the nuclear medicine functional imaging modalities, single-photon emission computed tomography and positron-emission computed tomography, have been used. This article reviews the studies performed in radiotherapy that used these modalities, and attempts to stimulate further interest in this topic.

Postmastectomy radiotherapy: toxicities and techniques to reduce them.

The role of locoregional radiation therapy after mastectomy is controversial. It reduces the risk of tumor relapse, improves breast cancer-specific survival and possibly overall survival, but has potential morbidity. This article reviews the technical aspects of postmastectomy radiation therapy and its associations with treatment-related morbidity. We consider common problems that arise in the technical setup of radiation fields. Adverse effects of postmastectomy radiation therapy may be reduced or prevented by careful radiation treatment planning.

Variability of the depth of supraclavicular and axillary lymph nodes in patients with breast cancer: is a posterior axillary boost field necessary?

PURPOSE: To determine the variability of the depth of supraclavicular (SC) and axillary (AX) lymph nodes in patients undergoing radiation therapy for breast cancer and to relate this variability with the patient's anterior/posterior (A/P) diameter. The dosimetric consequences of the variability in depth are explored and related to the need for a posterior axillary boost field. METHOD AND MATERIALS: In 49 patients undergoing treatment-planning computed tomography (CT) scanning in the treatment position, the maximum depth of the SC and AX lymph nodes was measured on CT images. The A/P diameter was measured at the location of the SC and AX, respectively. The relationship between the SC/AX lymph node depth and patient diameter was determined using linear regression. For an anterior SC and AX field, the relative dose to the SC and AX lymph nodes were calculated for a 6 MV photon beam. RESULTS: The maximum depth of the SC lymph nodes ranged from 2.4 to 9.5 cm (median, 4.3 cm). The depth was less than 3 cm in 4 patients, 3-6 cm in 39 (80%), and greater than 6 cm in 6 patients. There was a linear relationship between the SC lymph node depth and the A/P diameter. The depth of the SC lymph nodes in cm equals approximately one-half of the A/P diameter minus 3.5 (r(2) = 0.69). In 94% (46 of 49) of patients, the SC lymph node depth was between one-fifth and one-half of the A/P diameter. The depth of the axillary lymph nodes ranged from 1.4 to 8 cm (median, 4.3 cm). The depth was less than 3 cm in 8 patients, 3-6 cm in 32 (65%), and greater than 6 cm in 9 patients. The AX lymph node depth in cm equals approximately one-half of the A/P diameter minus 3 (r(2) = 0.81). In all patients, the AX lymph nodes were shallower than mid-depth. The depth of the SC and AX lymph nodes was within +/- 1 cm in 53% (26 of 49) of patients. The AX lymph nodes were located at >/= 1 cm shallower or greater depth than the SC in 24.5% (12 of 49) and 22.5% (11 of 49) of patients, respectively. If an anterior 6-MV beam only is used to treat the SC and AX lymph nodes in these 49 patients, the dose to the AX is within +/- 5% of the SC dose in 53% (26 of 49) patients and is 90% or more of the dose delivered in the SC in 90% (44 of 49) of patients. CONCLUSION: The maximum depth of the SC and AX lymph nodes varies widely and is related to the patient's size represented by the A/P diameter. In most patients, the AX lymph nodes lie at approximately the same depth or shallower than the SC. Therefore, the rationale for a posterior axillary boost field needs to be further assessed. When the AX and SC lymph nodes are deep, opposed supraclavicular and axillary fields and/or the use of a higher energy beam might be reasonable.

A practical and easy method to locate the first three internal mammary lymph node-bearing areas.

PURPOSE: To assess the distance from a clinically recognized anatomic landmark to the different costocondral interspaces in female patients to facilitate the design of radiation fields intended to include specific internal mammary nodal areas. METHODS AND MATERIALS: The distance from the suprasternal notch (SSN) to the caudal portion of the first through fourth interspace was measured on a computer display of the chest skeleton of 65 female patients with left-sided breast cancer. The relationship between these distances and bone size (sternal length and standing height) was assessed via linear regression. In 21 of the 65 patients where myocardial perfusion imaging of the heart was available, the relationship between the location of the 3rd costochondral interspace and the left ventricle was assessed. RESULTS: In 90% of patients (59/65), the first, second, third, and fourth interspace were within 5, 8.5, 11, and 14 cm of the SSN, respectively. The SSN-interspace distances did not correlate well with sternal length (r = 0.28) or standing height (r = 0.31). In 20 of 21 patients (95%), the third interspace "shadowed" the cephalad aspect of the left heart ventricle. Median "shadowing" was 3 cm (range 0.5-6 cm). CONCLUSION: The caudal portion of the third costochondral interspace is < or = 11 cm caudal to the SSN in 90% of patients. These measurements can be used to clinically design radiation therapy fields intended to treat the upper three interspaces. The distance from the SSN to the 1st through 4th interspaces is not related to sternal length or to standing height. In patients with left-sided breast cancer, radiation treatment fields designed to include the internal mammary lymph nodes in the upper three interspaces may incidentally include a portion of the heart.

Assessing the cost-effectiveness of postmastectomy radiation therapy.

PURPOSE: To assess the cost-effectiveness of postmastectomy local-regional radiation therapy (RT) for patients with breast cancer with regard to local-regional relapse (LRR) and quality-adjusted life years (QALY). METHODS AND MATERIALS: Data from the literature are used to estimate the risk of LRR, and the impact of RT on the risk of LRR and survival. The risk of LRR is related linearly to the number of positive axillary nodes 1% rate of LRR = 10 + (4 x number of positive nodes)]. RT reduces the risk of LRR by 67%. LRRs are treated with excision or biopsy followed by RT; half being controlled locally and half receiving additional salvage surgery and chemotherapy. Absolute improvements in 10-year overall survival due to RT are assumed to vary between 1 and 12%; and accrue linearly during the initial 10-year follow-up period. Professional and technical charges are used as a surrogate for costs. Money spent and benefits recognized in future years are discounted to 1997 values using a 3% annual rate. Quality factors are used to adjust for treatment, disease, and toxicity status. RESULTS: The cost per LRR prevented with the addition of routine postmastectomy RT is highly dependent upon the number of positive axillary nodes and ranges from $100,000-$200,000 for patients with 0-2 nodes, and $25,000-$75,000 for > or = 4 nodes. The cost per QALY gained at 10 years is $10,000-$110,000 for survival benefits > or = 3%. CONCLUSIONS: The cost per LRR prevented decreases with increasing numbers of positive axillary nodes. There is not a sharp cutoff at the < or = 3 vs. > or = 4 lymph node number, suggesting that using this cutoff for recommending or not recommending RT following mastectomy is not economically logical. The cost per QALY of $10,000-$100,000 compares favorably to that of other accepted medical procedures. Modest changes in the quantitative assumptions do not qualitatively alter the results. Concerns regarding costs should not generally preclude the use of postmastectomy RT.

Intracranial germinoma: the case for lower dose radiation therapy.

PURPOSE: To determine the optimal dose and treatment outcome of patients treated with radiation for intracranial germinoma. METHODS AND MATERIALS: Between 1975 and 1995, 40 patients with the diagnosis of intracranial germinoma were treated with radiation (RT) to the central nervous system. All patients received whole-brain (WB) RT (median dose: 32.4 Gy, range: 15-44.37 Gy) and a boost to the tumor volume (median total tumor volume dose: 52 Gy, range: 45-59.5 Gy). Thirty patients received RT to the spine (median dose: 26 Gy, range: 18.75-37.5 Gy). Four patients were treated with cisplatin-based chemotherapy and WB RT with a boost to the tumor volume (dose range: 51-54 Gy). A low-dose RT only group was defined as < or = 25.5 Gy to the WB (9 patients); < 50 Gy to the primary site (14 patients); and < 22 Gy to the spine (9 patients). Seventeen tumors were biopsy-proven germinoma, and 17 patients presented with multiple midline germinomas (MMG). Among 26 patients who had tumor markers measured, 27% had elevation of beta-human chorionic gonadotropin and by definition, no patient had an elevation of AFP. Twenty-four percent of 26 patients who had spine imaging or cerebral spinal fluid cytology had evidence of tumor seeding at diagnosis. The male to female ratio was 1.9:1. Median age at diagnosis was 14 years for male patients and 9.5 years for female patients (p = 0.02), (overall age ranges: 0.5-31 years). Median follow-up was 62 months (range: 3-226 months). Late effects of 29 patients with follow-up of > or = 20 months and adequate documentation in their medical records were analyzed. RESULTS: The 5-year actuarial rate of disease-free survival (DFS) and overall survival (OS) for biopsy-proven germinomas and presumed germinomas was 97%. No patient died of germinoma. There were no local failures regardless of the dose of RT, elevation of HCG tumor marker, or CSF dissemination at presentation. At presentation 22 patients had evidence of at least one endocrine abnormality. At follow-up there were no new patients diagnosed with an endocrine abnormality; however, 13 out of 22 patients had an increase in the number of endocrine deficiencies requiring hormone replacement. At presentation, 14 patients showed evidence of growth retardation. At follow-up there were no new cases of growth failure in the remaining patients. CONCLUSIONS: Germinomas are highly curable with RT alone. Lower doses of RT to the craniospinal axis without chemotherapy appear to produce equally effective DFS and OS as do higher doses of RT or combination chemotherapy and RT. Craniospinal RT may be indicated for patients with MMG or patients with evidence of spinal seeding. Long-term effects of growth retardation, and other endocrine deficiencies appear to be correlated with disease at presentation rather than solely with treatment.

Cardiac perfusion changes in patients treated for breast cancer with radiation therapy and doxorubicin: preliminary results.

PURPOSE: To determine the incidence and dose dependence of regional cardiac perfusion abnormalities in patients with left-sided breast cancer treated with radiation therapy (RT) with and without doxorubicin (Dox). METHODS: Twenty patients with left-sided breast cancer underwent cardiac perfusion imaging using single photon emission computed tomography (SPECT) prechemotherapy, pre-RT, and 6 months post-RT. SPECT perfusion images were registered onto 3-dimensional (3D) RT dose distributions. The volume of heart in the RT field was quantified, and the regional RT dose was calculated. A decrease in regional cardiac perfusion was assessed subjectively by visual inspection and objectively using image fusion software. Ten patients received Dox-based chemotherapy (total dose 120-300 mg/m(2)), and 10 patients had no chemotherapy. RT was delivered by tangent beams in all patients to a total dose of 46-50 Gy. RESULTS: Overall, 60% of the patients had new visible perfusion defects 6 months post-RT. A dose-dependent perfusion defect was seen at 6 months with minimal defect appreciated at 0-10 Gy, and a 20% decrease in regional perfusion at 41-50 Gy. One of 20 patients had a decrease in left ventricle ejection fraction (LVEF) of greater than 10% at 6 months; 2/20 patients had developed transient pericarditis. No instances of myocardial infarction or congestive heart failure (CHF) have occurred. CONCLUSIONS: RT causes cardiac perfusion defects 6 months post-RT in most patients. Long-term follow-up is needed to assess whether these perfusion changes are transient or permanent and to determine if these findings are associated with changes in overall cardiac function and clinical outcome.

Distinct mathematical behavior of apoptotic versus non-apoptotic tumor cell death.

PURPOSE: The presence or absence of a p53-dependent apoptosis response has previously been shown to greatly influence radiosensitivity in tumor cells. Here, we examine clonogenic survival curves for two genetically related oncogene transformed cell lines differing in the presence or absence of p53 and apoptosis. Solid tumor radiosensitivity patterns have been previously described for these lines. MATERIALS AND METHODS: Oncogene-transformed fibroblasts derived from E1A + Ras transfection of p53-wild-type or p53-null mouse embryonic fibroblasts were plated as single cells and irradiated at increasing radiation doses in single fractions from 1.5 to 11 Gy. Clonogenic cell survival assays were obtained. Survival data are fit to a linear-quadratic relationship: S = e(-alphaD-betaD2). Apoptosis was assessed and quantitated morphologically by staining with the fluorescent nuclear dye DAPI, by TUNEL assay for DNA fragmentation, and by measurement of apoptotic cysteine protease cleavage activity in cytosolic extracts. RESULTS: Whereas radiation triggers massive apoptosis in the presence of p53, it produces no measurable DNA fragmentation, apoptotic cysteine protease cleavage activity, or morphological changes of apoptosis in the cells lacking p53. These contrasting mechanisms of death display dramatically different quantitative behavior: log-survival of apoptotic cells is linearly proportional to dose (S = e(-alphaD)), whereas survival of non-apoptotic (p53 null) is linear-quadratic with a significant quadratic contribution. The surviving fraction at 2 Gy (SF-2) for p53-null cells was 70% verses 12% for p53-intact cells. CONCLUSIONS: In this system, apoptosis appears to exhibit a dominance of single-event which produces a very high alpha/beta ratio, and no significant shoulder; whereas non-apoptotic death in this system exhibits a comparatively small linear component, a low alpha/beta ratio, and a larger shoulder.

Treatment-related toxicity from a randomized trial of the sequencing of doxorubicin and radiation therapy in patients treated for early stage breast cancer.

PURPOSE: There is concern that breast cancer patients treated with left-sided radiation therapy (XRT) and doxorubicin (DOX) may have an increased risk of cardiac toxicity. In addition, the effect of different sequencing of XRT and chemotherapy (CT) on the likelihood of cardiotoxicity, as well as cellulitis, arm edema, or brachial plexopathy, is not well understood. We reviewed the records of patients treated on a randomized trial testing the sequencing of CT and XRT to determine if there was an increase in cardiac events or other complications in patients treated with a total dose of DOX of 180 mg/m2 and XRT, comparing patients with treatment to the left breast and the right breast, and comparing patients treated with initial CT and initial RT. MATERIALS AND METHODS: From June 1984 to December 1992, 244 patients with clinical stage I or II breast cancer were randomized following conservative surgery to receive CT (4 cycles of CAMFP at 3 week intervals) either before or after XRT (45 Gy to the entire breast, followed by a boost of 16 Gy; nodal radiation therapy was optional). Two hundred thirty-one patients were evaluable for the development of cardiac toxicity. The median age at diagnosis was 45 years (range, 20-68). CT doses were: doxorubicin, 45 mg/m2 IV bolus, d 3; methotrexate, 200 mg/m2 IV, d 1 and 15; 5-fluorouracil, 500 mg/m2 IV, d 1; cyclophosphamide, 500 mg/m2 IV, d 1; prednisone 40 mg p.o., d 1-5. A cardiac event was defined as a myocardial infarction or clinical evidence of congestive heart failure. Median follow-up time was 53 months. RESULTS: No cardiac events were observed for patients with either left- or right-sided breast cancer. The sequencing of CT and XRT had no significant effect on the risk of cardiac toxicity, cellulitis, arm edema or brachial plexopathy. CONCLUSIONS: We observed no evidence of an increased risk of cardiac toxicity from the addition of left breast tangential irradiation to DOX at a total dose of 180 mg/m2. Additional follow-up is needed to exclude possible late events. In addition, the sequencing of CT and XRT does not appear to affect the risk of cellulitis, arm edema, or brachial plexopathy.