Quality of life after surgery, external beam irradiation, or brachytherapy for early-stage prostate cancer.

BACKGROUND: The primary treatments for clinically localized prostate cancer confer equivalent cancer control for most patients but disparate side effects. In the current study, the authors sought to compare health-related quality of life (HRQOL) outcomes after the most commonly used treatments. METHODS: A total of 580 men completed the Medical Outcomes Study Short Form-36, the University of California-Los Angeles (UCLA) Prostate Cancer Index, and the American Urological Association Symptom Index before and through 24 months after treatment with radical prostatectomy (RP), external beam radiation therapy (EBRT), or brachytherapy (BT). RESULTS: General HRQOL did not appear to be affected by treatment. Obstructive and irritative urinary symptoms were more common after BT (P<.001). Urinary control and sexual function were better after EBRT than BT (P<.001 and P=.02, respectively) and better after BT than RP (P<.001 and P=.01, respectively). Among potent men, recovery of sexual function was best after EBRT and was equivalent after bilateral nerve-sparing surgery or BT. Sexual bother was more common than urinary or bowel bother after all 3 treatments. Bowel dysfunction was more common after EBRT or BT than RP (P<.001). CONCLUSIONS: In the current study, treatment for localized prostate cancer was found to differentially affect HRQOL outcomes. Urinary control and sexual function were better after EBRT, although bilateral nerve-sparing surgery diminished these differences among potent men undergoing RP. BT caused more obstructive and irritative symptoms, while both forms of radiation caused more bowel dysfunction. These results may inform medical decision-making in men with localized prostate cancer.

The biological effectiveness of antiproton irradiation.

BACKGROUND AND PURPOSE: Antiprotons travel through tissue in a manner similar to that for protons until they reach the end of their range where they annihilate and deposit additional energy. This makes them potentially interesting for radiotherapy. The aim of this study was to conduct the first ever measurements of the biological effectiveness of antiprotons. MATERIALS AND METHODS: V79 cells were suspended in a semi-solid matrix and irradiated with 46.7MeV antiprotons, 48MeV protons, or (60)Co gamma-rays. Clonogenic survival was determined as a function of depth along the particle beams. Dose and particle fluence response relationships were constructed from data in the plateau and Bragg peak regions of the beams and used to assess the biological effectiveness. RESULTS: Due to uncertainties in antiproton dosimetry we defined a new term, called the biologically effective dose ratio (BEDR), which compares the response in a minimally spread out Bragg peak (SOBP) to that in the plateau as a function of particle fluence. This value was approximately 3.75 times larger for antiprotons than for protons. This increase arises due to the increased dose deposited in the Bragg peak by annihilation and because this dose has a higher relative biological effectiveness (RBE). CONCLUSION: We have produced the first measurements of the biological consequences of antiproton irradiation. These data substantiate theoretical predictions of the biological effects of antiproton annihilation within the Bragg peak, and suggest antiprotons warrant further investigation.

Modeling growth kinetics and statistical distribution of oligometastases.

The kinetics of development of micrometastases, and especially of small numbers of metastases (oligometastases), was explored by using simple assumptions to develop concepts that may be useful for framing future research. The conclusions depend on the assumptions and hence must be considered speculative. It is assumed that beyond a threshold size for initiation of metastatic spread, which varies widely from tumor to tumor, the rate at which a primary tumor sheds new metastases increases exponentially, in parallel with its exponential growth. This increasing rate of release of new metastatic clonogens from the primary tumor is accompanied by a similar exponential growth of each of the micrometastases newly established at a secondary site. This creates a log-log linear relationship between the volume distribution of metastases and number of metastases, there being one largest metastasis followed by an exponentially expanding number of logarithmically smaller micrometastases. For example, if the micrometastases and the primary tumor grew at the same rate for 6 doublings after initiation of the first metastasis, then the primary tumor would have increased its volume by a factor of 64 (2(6)) and would be shedding metastatic clonogens at 64 times the initial rate. The first metastasis would undergo 6 doublings and contain 64 cells; the succeeding 2 metastases, released as the primary doubled in volume, would undergo 5 doublings and each would contain 32 cells; and so forth down to the 64 most recently developed single-cell metastases. However, the growth rate of metastases is expected to be faster than that of the primary tumor so that the rate of increase in volume of the micrometastases would be faster than the rate of increase in their numbers (through release of new metastases from the primary). Thus, although the log-log linear relationship is maintained, the slope of the volume frequency curve is changed; if the micrometastases grew 5 times faster than the primary, the slope would change by a factor of 5. Removal of the primary tumor as a source of new metastases truncates the expansion in numbers of metastases without affecting the growth rate of existing micrometastases, with the result that the volume-frequency relationship is maintained but the whole curve is shifted to larger volumes as micrometastases grow toward clinical detectability. The development of an oligometastatic distribution requires that the exponential expansion in the number of new metastases be stopped by eliminating the primary tumor soon after the first metastasis is shed. A cell destined to become part of an oligometastatic distribution had just been newly deposited at its metastatic site at the time the primary tumor was removed and must undergo about 30 doublings to become clinically detectable as an overt metastasis (2(30) or 10(9) cells). Thus, the time interval between removal of the primary and subsequent appearance of oligometastases will be toward the upper end of a distribution of "metastasis-free" intervals for its particular class of tumor. The actual time to appearance of a solitary metastasis, or of oligometastases, in any particular patient will depend on the growth rate of the metastases in that individual but will always require about 30 volume doublings. An apparently solitary metastasis appearing synchronously with the primary tumor is unlikely to be solitary because, to do so, it would have to have undergone about 30 doublings without further release of metastatic clonogens from the primary that is, in our model, within 1 doubling in volume of the primary tumor. For the same reason, a synchronous or early appearing oligometastatic distribution is unlikely, but if it were to exist, there would be a steep gradient between the volumes of largest and smallest metastases because the growth rate of the micrometastases to produce synchronous metastases, without having further metastases shed from the primary, would have to be fast (up to 30x) relative to the growth rate of the primary. Conversely, a steep gradient in volumes of successive echelons of metastases reflects fast growth of metastases relative to the primary and favors the possibility of an oligometastatic distribution. This ratio of growth rates of metastases to primary is defined by the slope of the log-log curve for the volume-frequency distribution of metastases, which, in clinical practice, is difficult to determine over a wide range and is, by definition, essentially impossible for oligometastases. However, the volume-frequency relationship, measured over a wide range, is the same as the ratio of the volume of the largest to second-largest metastases in an oligometastatic situation. For example, if the metastasis doubled 5 times faster than the primary, the largest metastasis would be larger by 5 doublings than its closest follower(s), that is, by a factor of 2(5) or 32, equivalent to a 3.2-fold difference in diameter if the metastases were spherical. Alternatively, if an initially solitary and measurable metastasis is subsequently joined by measurable followers, the number of volume doublings separating successive echelons in the series can be determined directly, and the larger the difference (measured in doublings), the greater the probability that there will be a limited, oligometastatic condition (ie, in clinical terms, subsequent metastases will stop appearing after the large leader metastasis and a short succession of followers have been removed at 1 or more operations). In summary, the probability of there being an oligometastatic distribution is increased as the interval between removal of the primary tumor and appearance of metastases lengthens. It is also more likely the faster the metastases are growing relative to the growth rate of the primary tumor before its removal. Effective systemic cytotoxic treatment (eg, chemotherapy, hormonal manipulation, biological agents) given in the perioperative period, or concomitantly with radiation therapy for the primary tumor, would truncate the volume-frequency distribution toward an oligometastatic one by eliminating the smallest, most recently formed "tail-ender" metastases. That process, which only occurs at the threshold volume of the primary at which metastases are first initiated, would not be influenced by whether surgery or radiation therapy was chosen to treat the primary tumor, regardless of the overall duration of radiation therapy. Chemotherapy adjuvant to surgery is not usually indicated in the curative treatment of solitary or oligometastases because they represent a truncated distribution with few or no stragglers. If subclinical stragglers exist, they would usually be relatively large and, even though subclinical, too large to be cured by chemotherapy. Exceptions would be early rapidly growing oligometastases, especially from a slowly growing primary, or solitary metastases from an unknown primary where second echelon metastases, if they exist, may still be small. Otherwise chemotherapy could be postponed and used for palliative growth restraint of unusually large and/or numerous stragglers.

The biological basis of fractionation.

A few important concepts in radiobiology are illustred. The cell survival, the concept of the biologically effective dose, the basis of fractionation in radiotherapy are considered. Slow tumor regression after irradiation is not an indication of treatment failure, and the rate of regression is not , in general, prognostic. Dose volume histograms provide many data for predicting tumor control and side effects. The magnitude of a dose reduction in the tumor is the major determinant of decline in tumor control probability. Escalation of dose to hypoxic foci may be beneficial. Basic knowledge of these concepts is essential for daily radiotherapy practice and for all radiation oncologists.

The efficacy of hyperbaric oxygen therapy in the treatment of radiation-induced late side effects.

PURPOSE: We investigated the efficacy of hyperbaric oxygen therapy (HBOT) in the management of patients with radiation-induced late side effects, the majority of whom had failed previous interventions. METHODS AND MATERIALS: Of 105 eligible subjects, 30 had either died or were not contactable, leaving 75 who qualified for inclusion in this retrospective study. Patients answered a questionnaire documenting symptom severity before and after treatment (using Radiation Therapy Oncology Group criteria), duration of improvement, relapse incidence, and HBOT-related complications. RESULTS: The rate of participation was 60% (45/75). Improvement of principal presenting symptoms after HBOT was noted in 75% of head-and-neck, 100% of pelvic, and 57% of "other" subjects (median duration of response of 62, 72, and 68 weeks, respectively). Bone and bladder symptoms were most likely to benefit from HBOT (response rate, 81% and 83%, respectively). Fifty percent of subjects with soft tissue necrosis/mucous membrane side effects improved with HBOT. The low response rate of salivary (11%), neurologic (17%), laryngeal (17%), and upper gastrointestinal symptoms (22%) indicates that these were more resistant to HBOT. Relapse incidence was low (22%), and minor HBOT-related complications occurred in 31% of patients. CONCLUSION: Hyperbaric oxygen therapy is a safe and effective treatment modality offering durable relief in the management of radiation-induced osteoradionecrosis either alone or as an adjunctive treatment. Radiation soft tissue necrosis, cystitis, and proctitis also seemed to benefit from HBOT, but the present study did not have sufficient numbers to reliably predict long-term response.

Where next with preoperative radiation therapy for rectal cancer?

PURPOSE: The basic question for radiation oncologists is what we hope to achieve from treatments that are adjuvant to surgery: better local (pelvic) control and, hopefully, because of that, fewer metastases. Chemotherapy could add to the local effect of irradiation and may also decrease distant metastases directly. Selection criteria for individual treatment could enhance the therapeutic index. LOCAL CONTROL: Total mesorectal excision reduces the incidence of local recurrence, but preoperative (chemo) radiation is still indicated for more advanced tumors (T3-T4) and for lymph node involvement. Pelvic recurrences arise from tumor clonogens residual beyond the surgical margins. Thus, the practice of shrinking fields to boost the dose to the primary tumor makes no sense, except for tumors that invade residual structures, such as the sacrum. Subclinical disease beyond the future surgical margins grows more quickly than the primary tumor, and hence treatment should be as intense as tolerable. A short treatment course (e.g. 5 x 5 Gy) is desirable, but this regimen, which is currently the gold standard, should be compared (as in the recently closed randomized Polish trial) with higher-dose, longer-duration chemoradiotherapy regimens. The recently closed EORTC trial 22921 examines the benefit of pre- and postoperative chemotherapy combined with a long schedule of radiation. Likewise, continuous infusion of a cycle-active agent rather than bolus administration is a logical addition to radiation therapy in the treatment of fast-growing subclinical tumor extensions. SYSTEMIC DISEASE: The reduction in distant metastasis rates attributable to adjuvant chemotherapy varies greatly among reports. If the reduction is of the order of 10-25%, the efficacy of chemotherapy equates to as little as about 5 to 12.5 Gy and not more than 20 Gy of total body irradiation. INTERVAL BETWEEN RADIATION THERAPY AND POSTRADIATION SURGERY: Early excision after preoperative irradiation would be desirable if the primary tumor were still disseminating viable metastatic clonogens. Most tumors do not metastasize until they contain enough viable clonogens to render them clinically detectable. A dose of 10 Gy in 2 Gy fractions reduces at least 30-fold the absolute number of viable clonogens in the primary tumor, to levels that do not yield metastases from the untreated tumor. After a dose of 44-50 Gy in 2 Gy fractions, there is little chance that the surviving tumor clonogens could regrow to a metastasis-yielding volume in any reasonable radiation-surgery interval. Thus there is no tumor-related necessity for early postradiation surgery. The importance of the interval between radiation and surgery is currently being addressed in a Swedish randomized trial. PROGNOSTIC AND PREDICTIVE CHARACTERIZATION: Tumor volume should be included in the staging system. There are many tumor- and host-related characteristics that can be used to fingerprint the tumor to help select appropriate individual treatment.

Initial clinical results of stereotactic radiotherapy for the treatment of craniopharyngiomas.

The efficacy and toxicity of stereotactic radiotherapy (SRT) for the treatment of craniopharyngioma has been retrospectively evaluated in 16 patients. The median tumor diameter was 2.8 cm (range 1.5-6.1) and the median tumor volume was 7.7 cc (range 0.7-62.8). SRT was delivered to a single isocenter using a dedicated 6 MV linear accelerator to patients immobilized with a relocatable stereotactic head frame. The three-year actuarial overall survival was 93% and the rate of survival free of any imaging evidence of progressive disease was 75%. The three-year actuarial survival rates free of solid tumor growth or cyst enlargement were 94% and 81% respectively. Our results suggest that SRT is a safe and effective treatment approach for patients with craniopharyngioma. Long-term follow-up is required to determine whether the normal tissue-sparing inherent with SRT results in reduction of the neurocognitive effects of conventional radiotherapy for craniopharyngioma. SRT can be delivered to craniopharyngioma that may be difficult to treat with stereotactic radiosurgery due to proximity of the optic chiasm. Further clinical experience is necessary to determine the clinical utility of beam shaping in the setting of SRT.